Rockwell Automation 1756-OF8I ControlLogix Eight-channel Isolated Analog I/O Modules - Manual (Page 15)

Rockwell Automation Publication 1756-UM540A-EN-P - May 2014 15
Isolated Analog I/O Module Operation in the ControlLogix System Chapter 1
The input module broadcasts data to the chassis backplane immediately after
the scan:
• When the module resides in the local chassis, the controller receives the
data immediately.
• When the module resides in a remote chassis, the time elapsed before the
controller receives it depends on the configuration of the network
connecting the local and remote chassis.
For more information, see Input Modules in a Remote Chassis .
Input Modules in a Local Chassis
When an input module resides in a local chassis, as shown on page 11 , after the
input module broadcasts data to the chassis backplane, the controller receives
it immediately.
Input Modules in a Remote Chassis
When an input module resides in a remote chassis, as shown on page 12 , it is
considered remote input module.
At the RPI, the following events occur.
1. The remote input module scans its channels for input data.
2. The remote input module broadcasts the data to its backplane.
3. The network communication module in the chassis with the I/O module
sends the data over the network to the controller.
Broadcast Method
The isolated analog input module broadcasts data by using one of the following
connection methods:
• Multicast - Data is sent to all network devices
• Unicast - Data is sent to a specific controller depending on the
module’s configuration
For more information on guidelines for specifying RPI rates, see the Logix5000
Controllers Design Considerations Reference Manual, publication
1756-RM094 .